Detector development and data analysis of the high energy particle detectors on-board the CSES satellites

The China Seismo-Electromagnetic Satellite (CSES) is a Chinese-Italian space mission aimed at studying the electromagnetic, plasma, and particle environment in low Earth orbit with the main purpose of correlating perturbations observed in the magnetosphere with solar and terrestrial activity. Two satellites of the CSES constellation are currently in orbit: CSES-01, launched on February 2, 2018, which has been operating nominally since then, and CSES-02, launched on June 14, 2025 in commissioning phase up to end 2025. Among the different instruments onboard the CSES satellites, the High Energy Particle Detectors (HEPD-01 and HEPD-02) developed by the Italian collaboration Limadou. Both instruments have the capability of measuring the particle environment distinguishing electrons with energies in the range 3 to 100 MeV, protons from 30 to 200 MeV, and light nuclei up to about 300 MeV/nucleon. In this thesis a thorough analysis of HEPD-01 data was conducted to measure proton fluxes based on geomagnetic latitude during periods of low and high solar activity. The analysis identified distinct particle populations, confirming previous findings and expanding observations to lower rigidities. This analysis lays the groundwork for future missions in understanding instrumentation, data analysis, and physics aspects. In addition, the design, testing, and characterization of the performance of the HEPD-02 detector, an upgrade from HEPD-01, developed to extend the measurable energy range and enhance the detector’s overall performance, are described. Procedures were also developed to characterize photomultiplier tubes and assign them to specific counters. Extensive tests confirmed the linearity and efficiency of the scintillating counters after integration in HEPD-02. Finally, the in-orbit commissioning activities of HEPD-02 after the CSES-02 launch enabled the detector optimization and in-flight performances verification in preparation for the start of an exciting scientific observation phase.